The purpose of this study is twofold. The first goal is to study the utility of positron emission tomography of the heart (with provocative testing) in the diagnostic evaluation of chest pain in postmenopausal women, particularly women with angiographically normal coronary arteries. Secondly, the noninvasive nature of the PET scan will allow us to assess the effect of long-term hormonal replacement on coronary blood flow and coronary vasoreactivity.